Also, forgot to add: list the dataset and note the management class (MGMTCLAS).
This will tell you how DFSMShsm is managing the dataset and whether space is
routinely being released.
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Michael Watkins
Sent: Wednesday, February 21, 2024 4:07 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Something keeps releasing space on a large (annual) DS
CAUTION: This email originated from outside of the Texas Comptroller's email
system.
DO NOT click links or open attachments unless you expect them from the sender
and know the content is safe.
"ALLOC DDN(CHG$$OT) DSN('<dsn>') MOD CATALOG REUSE", "SPACE(300,30) CYLINDERS
RECFM(V,B) LRECL(304) BLKSIZE(27998)"
Yes, always allocate anything other than a very small dataset in cylinders.
Also, keep in mind that an extended PS appends a 32-byte suffix onto every
block of data (an 8-byte prefix onto blocks of datasets allocated as
DSNTYPE=LARGE). Specifying BLKSIZE=27998 may mean that you only have 1 block on
each virtual 3390 track on your RAID storage frame. Perhaps code BLKSIZE=0 and
let the system determine the BLKSIZE.
One advantage extended format datasets enjoy is that up to 123 extents can be
allocated on each volume, although the 65,535 tracks (4,369 CYLs) per volume
z/OS limit is still adhered to.
Unless there are limits imposed by your application, do not hesitate to span up
to the z/OS limit of 59 volumes or take advantage of zEDC compression.
Also: Not all applications, particularly those that have a special internal
format (like SAS) or that write their own I/O (like Adabase) can use extended
format datasets.
Inquire with your storage manager whether there is an existing DATACLAS that
meets your needs. Or explain your issues and perhaps the storage manager will
design a DATACLAS for you.
Good luck!
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Mike Schwab
Sent: Wednesday, February 21, 2024 2:58 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Something keeps releasing space on a large (annual) DS
CAUTION: This email originated from outside of the Texas Comptroller's email
system.
DO NOT click links or open attachments unless you expect them from the sender
and know the content is safe.
Its probably doing a release.
Do a cylinder allocation to at average 7 tracks after release.
Defragment to consolidate extents weekly / twice a week / MWF / daily.
On Wed, Feb 21, 2024 at 11:45 AM Bob Bridges
<00000587168ababf-dmarc-requ...@listserv.ua.edu> wrote:
I'm not a sysprog (just a security geek), but I can at least allocate datasets,
and at the start of this year it fell to me to allocate a new dataset in which
are logged all changes made in the security system. Past year's log are in the
12000-track range, so I started with a smaller allocation while I took the time
to talk to our sysprog about space requirements. It's populated from a daily
production job, by the way.
When I re-allocated it, on his advice I tried a multi-volume and extended
allocation (PS-E). Almost immediately the job started bombing, claiming that
the first four volumes it tried didn't have the necessary space to add an
extension. The sysprog is puzzled - says it should have looked in volumes that
DO have the space, not the ones that don't.
Second attempt (I don't count the temporary smaller allocation) I kept PS-E but
dropped the multi-volume requirement. I've never done one of those anyway, and
don't trust 'em. The system promptly dropped the extra tracks I allocated, and
a day or two later the job started bombing with a B37-04.
Third attempt: Forget PS-E (I'm unfamiliar with that too) and just used
SPACE=(TRK,(9000,1000)). That seemed to work for a whole week, but I just
noticed that something, somewhere, has released extra space AGAIN; 3.4 tells me
it's now 1960 tracks and 83%. The job isn’t bombing yet; some time later in
the year I'm guessing it's going to.
Pardon my frustration: WHAT THE HECK IS GOING ON? Why does it keep releasing
space although I never specified RLSE? The sysprog doesn't know either - but
he's an external contractor who just took over the system a few months ago and
if it's something simple he may not be aware yet of ... I dunno, something in
SMS maybe?
Some wrinkles that may or may not be relevant:
1) The dataset is written using a REXX exec that calculates the DSN by
reference to the current year. This relieves folks from having to update the
JCL every year, but maybe something about the way the exec does the allocate is
causing the problem? I'm guessing not, because as far as I now this job has
run correctly for years. But just in case:
"ALLOC DDN(CHG$$OT) DSN('<dsn>') MOD CATALOG REUSE", "SPACE(300,30) CYLINDERS
RECFM(V,B) LRECL(304) BLKSIZE(27998)"
2) I don't know anything about SMS, but could something there be releasing
space?
3) What IS extended PS, anyway? I'm told it allows more than 16 extents, but
a) how many more? And b) how else is it different?
4) I allocated the dataset each time using not batch JCL but 3.2 ... expecting
there's no difference.
---
> Bob Bridges, robhbrid...@gmail.com, cell 336 382-7313
>
/* Law #6 of combat operations: If it's stupid but it works, it isn't stupid.
*/
> ----------------------------------------------------------------------
> For IBM-MAIN subscribe / signoff / archive access instructions, send
> email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
--
Mike A Schwab, Springfield IL USA
Where do Forest Rangers go to get away from it all?
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions, send email to
lists...@listserv.ua.edu with the message: INFO IBM-MAIN
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions, send email to
lists...@listserv.ua.edu with the message: INFO IBM-MAIN
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
